This invention concerns a device to handle ladles serving the casting zone. To be more exact, this invention concerns a device suitable to move ladles independently from a tapping position at a furnace, whether the furnace be an electric furnace or of another type, to a casting position after passing through intermediate stations for refining the steel or molten material in general and for cleaning the ladles themselves.
The device may be applied to zones for continuous casting, zones for casting into ingot moulds or zones for mixed casting with or without zones for emergency casting.
Ladles are positioned at present below a smelting furnace and then are filled and moved to the casting zone. For such movement a bridge crane is used, or else the ladle is run on appropriate rails and, if necessary, undergoes a series of auxiliary operations before reaching the casting zone or, viceversa, before returning to the furnace.
This situation entails a set of drawbacks in that the times of the operations are not coordinated and are relatively long, the various steps are not standardized and there is not an optimum process control.
The results obtainable are therefore far from being those which can theoretically be attained since all the above factors entail a series of drawbacks, above all as regards the lack of standardization of the various steps, increased downtimes and the lack of a continuous, automatic control of the process itself.
GB No. 677,023 is known and provides for a system to handle a ladle along a substantially circular path served by a bridge crane or hoist. Along this circular path the ladle undergoes a plurality of treatements, but GB No. 677,023 does not make exactly clear how the ladle is handled (rotation, tilting, overturning, etc.).
Beside its requirement for independent means (a lifting crane or hoist of a considerable size) the system disclosed in GB No. 677,023 imposes a plurality of restrictions, of which the main ones are as follows: the considerable difficulty of its use in cooperation with continuous casting precisely because of the need to lift the ladle; handling not tied to precise technical timings and therefore not optimum in relation to requirements of the manufacturing cycle; the need to have many ladles available at one and the same time so as to maintain the processing times imposed by the system; the employment of closure means (position 9) which are not suitable for modern casting systems; a very great and therefore uneconomical area is taken up; the systems for handling (tilting, overturning, etc.) the ladle itself are not disclosed in GB No. 677,023.
A system according to GB No. 677,023 can therefore not be installed in view of present requirements regarding time, quality and space relative to modern casting plants, but above all to problems of automation which have had to be considered for several years now.
In the final analysis, GB No. 677,023 is just a description of normal steps performed in a traditional steel mill; the one single new feature is that these steps are carried out along a circular plan.
FR No. 1.551.721 is also known but tackles only the problem of continuous casting in a continuous casting plant, that is to say, it tends to overcome the limitation of continuity of casting proper to a ladle because of its defined content. It provides for ladles, charged with molten metal in another part of a steel mill, to be brought to the device and put thereupon in replacement of empty ladles.
The device disclosed in FR No. 1.551.721 in fact replaces the normal casting carriages, in comparison with which it is still not possible to understand whether the device provides advantages or not; in fact, both systems are still employed.
The device of FR No. 1.551.721 can be applied only to continuous casting plants, and, if necessary, this can be understood from the description of the patent itself.
Owing to its specific destination and to the idea of the solution which it has generated, the device of FR 1.551.721 does not provide, for example, for rotation of the ladle on its own axis, nor for auxiliary operations at the molten bath, nor does it disclose how operations to restore the ladle can take place since, among other things, such operations are not even provided for.
Thus, besides having different purposes from those of GB No. 677,023, FR No. 1.551.721 does not discloses anything which can be integrated readily and obviously with the disclosures of GB No. 677,023.
In fact, the operational thinking of GB No. 677,023 can in no way be transferred to or integrated with the operational thinking of FR No. 1.551.721 as regards the different operating means or as regards the different intermediate operating purposes or different functional requirements which either of these patents tend to solve.
FR No. 1.578.603 and FR No. 1.371.056 conform substantially to FR No. 1.551.721.
FR No. 2.437.258 is substantially the same as FR No. 1.551.721 but, as compared to the latter, provides for full ladles to be taken independently and empty ladles to be discharged independently.
DE OS No. 2.028.078 is also known and discloses one single arm (in contrast to FR No. 1.551.721 which discloses two independent arms) extending symmetrically in relation to the axis of rotation and also envisages that the ladle can be overturned by a certain angle.
The Italian trade journal "La rivista dei Cuscinetti" (Journal of Bearings), no.215, shows on pages 1 to 3 an embodiment with stationary positioned arms which are yet capable of moving the ladle vertically. In this embodiment too, as in all those described above an in all existing embodiments which have not been cited here as they repeat the same concept, the ladle is loaded onto the device only after it has been charged with molten metal elsewhere and after it has been brought from the tapping zone to the zone in which the device operates.
It should be noted that hitherto no evolutive steps have been taken beyond FR No. 1.551.721, beyond GB No. 677,023, or beyond the other patents detailed herein, indicating the unchanging nature of the vision and reasoning of persons skilled in this field. This is so, notwithstanding the fact that the problems which the present invention tends to overcome have taken on considerable importance for many years now.